Anaerobic digestion is an important technology in organic wastewater treatment. Anaerobic reactors are the heart of the anaerobic processes. Traditional and normally used anaerobic reactors in wastewater treatment include up-flow anaerobic sludge bed (UASB) reactors, anaerobic filters, fluidized bed reactors, and so on. The reactors mentioned can be used in treatment of a quite wide range of wastewater and can reach an acceptable level of contaminant removal. However, these reactors have some disadvantages of larger sizes, lower and unstable load capacities, unusable byproducts produced, filler plugging, costly maintenance, etc. Recently developed internal circulation (IC) reactor is a development of a UASB reactor. An IC reactor shows a number of advantages over the traditional anaerobic reactors. In an IC reactor, the internal flow is caused by gas flowing up through an “up flow pipe” and liquid flowing down through a “down flow pipe”. The flow causes internal circulation in reactor and the circulation depends on the contaminant content (for example, Chemical Oxygen Demand—COD) of wastewater being treated, so that the internal circulation is to some extent controllable.
The IC reactors give a number of improvements above traditional UASB reactors and overcome the problems, to some extent, in traditional anaerobic reactors. These include: (1) Mass transfer between particulate sludge and organic contaminant is enhanced by the internal circulation so that the load is increased and lower capital investment with a smaller size can be achieved. (2) Hydraulic retention time is reduced. (3) Increased load and more stable operation. However, some problems still exist in IC reactors, which are: (1) Sludge addition is not flexible in the operations, which reduces the efficiency of contaminant removal. (2) Internal circulation is difficult to begin in starting up of the reactor and in the operations. These problems reduced the efficiency of IC reactors.
Additional improved and modified structure and design to combine with the improvements addressed above are required to overcome the disadvantages to increase efficiency of anaerobic reactors.
The following Patents and Reference are cited:
U.S. Pat. No.:20030150786 (Application No.)VerinkEuropean Patent:EP 1 205 442 A1VA TECH WABAG DeutschiandGmbH &Co. KG (Applicant)